Provided are resistive random access memory (ReRAM) cells forming arrays and methods of operating such cells and arrays. The ReRAM cells of the same array may have the same structure, such as have the same bottom electrodes, top electrodes, and resistive switching layers. Yet, these cells may be operated in a different manner. For example, some ReRAM cells may be restively switched using lower switching voltages than other cells. The cells may also have different data retention characteristics. These differences may be achieved by using different forming operations for different cells or, more specifically, flowing forming currents in different directions for different cells. The resulting conductive paths formed within the resistive switching layers are believed to switch at or near different electrode interfaces, i.e., within a so called switching zone. In some embodiments, a switching zone of a ReRAM cell may be changed even after the initial formation.